DC (direct current) motors, and driver circuits to energize them, are well known. DC motors may be deployed for bi-directional operation, for example as a sled motor for an optical pickup in a computer optical disk drive. Usage of DC motors is common and there are many applications for them.
As shown in FIG. 1, using a previously developed driver circuit 40, a DC motor 300 may be energized for rotation in either clockwise or counter-clockwise direction and at various speeds responsive to the polarity and magnitude of the drive current. A BTL (balanced transformerless) circuit may be used. The motor may receive current from a PA (power amplifier) that is preceded in the drive circuit by a scaling circuit and a level-shifting circuit. The scaling circuit may deploy one or more attenuators and/or one or more amplifiers such as OpAmps (operational amplifiers). The level shifting and scaling circuits may be responsive to an analog signal generated by a DAC (digital to analog converter) which may be controlled by or incorporated into a microcontroller such as a DSP (digital signal processor). Typically in such a circuit, the DSP is responsive to a sensor that detects motor rotation or motor position and thus a closed loop control system for the motor may be formed.
In some applications, for example in consumer grade electronic devices, operation over a wide tolerance in input voltage, using cheaper components, and without performance degradation is desirable. In previously developed circuits, it may be necessary to adjust the level shifting circuit or the scaling circuit if it is required to accommodate wide variations in input supply voltage, for example, in a product variant. Alternatively, optimal performance may be compromised by design constraints, such as of multiple product variants.